next time when you arrive at the bus stops you frequent, make a note of the 5 digit bus stop number. with that, you will be able to get the arrival times of all buses at one particular stop through this link. kudos to the guy who took the effort to make our lives easier.

alternatively you can use SBS's online service but you will need to enter the bus number, the direction and bus stop you want. And if you already know the bus stop number, you will still need to enter the bus number. so might as well use the first link. i think SBS should just use the guy's link on their website.